The conformations, microdynamic behavior, and interactions with biologically important macromoleculaes of peptide hormones, analogues, derivatives and other biologically important peptides will be examined by a variety of biological activity and the conformations and microdynamic properties of the peptides will be sought, and the results will be used as a basis for preparing better hormone antagonists and more specific agonists, and for examining the chemical-physical basis of hormone action. Specifically labeled (deuterium, carbon-13, carbon-14, fluorine, etc.) derivatives of the neurohypophyseal hormones and biologically important analogues will be prepared. For this purpose, efficient procedures for synthesizing C13 and H2-labeled amino acids be sought. The deuterated and carbon-13 labeled hormones will be used in studies of the conformational and microdynamical behavior of these compounds, and of the interactions of the hormones with their carrier proteins in the neusecretory granules, the neurophysins. Nuclear magnetic resonance spectroscopy, circular dichroism, viscosity studies, binding studies, cross-linking experiments, and other chemical-physical methods will be used to develop a basis for understanding hormone action at the molecular level. The interaction of peptide hormones with their cellular and membrane receptors will be examined. Hormones or hormone glucagon, and oxytocin will be used in these studies. The design of hormone derivatives with properties useful for medical and other applications will be sought.